Field of the Invention
Aspects of the present invention relate to a power transmission apparatus capable of wirelessly supplying power to an electronic device, and a method for controlling power transmission.
Description of the Related Art
A wireless power transmission system is known in which power is wirelessly transmitted using an electromagnetic field resonance phenomenon or an electromagnetic induction phenomenon. In such a wireless power transmission system, when an electronic device that receives power is removed during power transmission, a power transmission apparatus is required to operate without any adverse effect on other devices and metals located in the neighborhood of the power transmission apparatus.
Japanese Patent Laid-Open No. 2011-45190 discloses a power transmission control device including: a control unit that controls power transmission of power to a power receiving device with a primary coil and a secondary coil by non-contact power transmission; and a communication process unit that performs communication control by communication between coils using the primary coil and the secondary coil. This power transmission control device is configured to set wireless communication between a power-transmitting-side wireless communication unit and a power-receiving-side wireless communication unit to a non-connected state when removal of the power receiving device is detected.
In the method disclosed in Japanese Patent Laid-Open No. 2011-45190, a power transmission apparatus detects a change in the waveform of an induced voltage signal (coil end signal) from the primary coil, thereby detecting removal of the electronic device. However, the waveform of the dielectric voltage signal may vary depending on, for example, transmission power to be output, a change in the load of the electronic device, or the position where the electronic device is placed. Accordingly, if removal of an electronic device is to be detected using only a change in the waveform of the induced voltage signal, it is difficult to accurately detect removal of the electronic device.